The present disclosure relates to an optical disc device that reads information recorded in optical disc medium such as CD, DVD, and Blu-ray Disc (registered trademark), a control method thereof, a program, and an information storage medium.
In recent years, various kinds of optical disc medium are used as information recording medium. To read information recorded in such optical disc medium, an optical disc device is used. The optical disc device includes an objective lens that focuses light on the optical disc medium. The optical disc device receives reflected light obtained by reflection of the light focused by the objective lens by the optical disc medium, to thereby read information recorded in the optical disc medium.
When the optical disc device reads information from the optical disc medium, spherical aberration correction of the objective lens needs to be carried out. For example, in an optical pick-up, a collimator lens is provided in order to correct the spherical aberration of the objective lens that focuses light on the optical disc medium. By properly adjusting a position of this collimator lens, the spherical aberration of the objective lens can be corrected and the light from the objective lens can be focused on the optical disc medium with high accuracy.
The optical disc device internally manages the position of the collimator lens as a value of a parameter called the SA parameter. An optimum value of this SA parameter varies depending on the kind, individual difference, and so forth of the optical disc medium as a reading target. Therefore, when an optical disc medium is newly set in the optical disc device, the device executes adjustment processing of the SA parameter before starting reading of information (refer to e.g. Japanese Patent Laid-Open No. 2003-16660). This adjustment processing is the following control. Specifically, first the optical disc device changes a setting value of the SA parameter in a settable range. Furthermore, the optical disc device attempts reading of information from the medium in each of three or more states in which different setting values are set, and evaluates an accuracy of information reading at the time. Then, the optical disc device calculates such a setting value of the SA parameter as to allow enhancement in the accuracy of information reading by using an evaluation values of the reading accuracy obtained corresponding to each of the plural setting values, and sets this calculated value as the value of the SA parameter.